Die cast zinc base alloy product



Patented Sept. 26, 1933 UNITED STATES DIE CAST ZINC BASE ALLOY PRODUCT John .R. Freeman, Jr., Waterbury, Conn., as-

signor to The American Brass Company, Waterbury Conn, a corporation of Connecticut No Drawing. Application December 17, 1931 Serial No. 581,777

2 Claims.

This invention relates to die cast zinc base alloy products and has for its object the provision as a new article of manufacture of improved zinc base alloy products of this nature.

5 The design of the usual type of die casting machine, such as the so-called plunger or gooseneck machines, is such that the mechanism is to a great extent completely immersed in the molten alloy to be cast. The mechanical requirements of the die casting process as carried out in the plunger or goose-neck machines are such that many of the working parts of the ma chine must be constructed of iron or steel. These metals are subject to attack by molten zinc and zinc alloys and it is known from experience that to minimize this attack sufiiciently in order to obtain reasonable life from the machines it is necessary that at least 0.25% of aluminum be present in the alloys. It is known further that aluminum when present in zinc base alloys even in amounts less than 0.25% causes a disintegration or intercrystalline corrosion to occur more especially in warm and humid atmospheres, but amounts less than 0.05 percent of aluminum may not be objectionable although it is preferred that the alloy be free from aluminum, or at least contain not more than 0.05 percent. Magnesium also when present in zinc base alloys may under certain conditions, more particularly when the alloy is free or substantially free from aluminum, I cause a similar disintegration or intercrystalline corrosion to occur. Zinc base alloys containing aluminum are also subject to change in strength,

more particularly in impact strength, with time even in the absence of moisture.

Improved zinc base alloys containing aluminum have been developed in which the degree of disintegration or intercrystalline oxidation has been reduced by the addition of elements other than aluminum such as copper and more particularly magnesium. A committee on die cast metals and alloys of The American Society For Testing Materials has recently conducted an extensive series of tests to determine the most suitable alloy or alloys for adoption as standard alloys for the industry. All of the alloys tested contained aluminum and of all the alloys tested only one alloy was found to be sufliciently stable, that is, free from disintegration or change in physical less than 0.05 percent magnesium may be preproperties with time. This zinc base alloy has the nominal composition of 4% aluminum, 3% copper and 0.05% magnesium, and the further requirement that the lead content shall be not greater than 0.01% and the cadmium and tin contents not greater than 0.005% respectively. It is specified also that the zinc used for the preparation of the alloy shall contain not more than 0.02% total impurities. The investigations of the above committee have shown that the use 6( of very pure zinc is essential because of the deleterious efiect of the impurities normally present in zinc, more particularly lead. It is known also that magnesium is essential in zinc alloys containing aluminum, even when very pure zinc is used to inhibit disintegration in humid atmospheres.

I have found that die cast zinc base alloy products made of an alloy of zinc and manganese and free or substantially free from aluminum and magnesium, more particularly an alloy containing from about 0.05% to about 10% manganese and preferably free from aluminum and magnesium, or containing less than 0.05% of aluminum and pared successfully and economically in a die casting machine in which the melting chamber is entirely separated from the casting mechanism. I have found that die cast zinc base alloy products containing the above noted amounts of manganese when free or substantially free from aluminum and magnesium are stable, that is, they do not change in physical properties with time even when subjected to hot humid atmospheres for long periods of time. The above range of manganese produces useful alloys, but the preferred range is from about 0.50% to about 2.0% of manganese.

For example there are given in the following tables the results of tests of a die cast zinc base alloy product prepared from a zinc manganese alloy substantially free from aluminum and magnesium, and of a similar die cast product of an alloy of zinc, copper, aluminum and magnesium.

In the table the properties given for product designated (A) are typical for the new die cast products free or substantially free from aluminum and magnesium for which Letters Patent are desired. The properties for product (B) are typical for die mu cast product containing aluminum at present widely used in the industry.

Composition of products Physical properties after exposure to water vapor for 10 days at a temperature of 95 C.

'gensiljel tElonga- Impa'ct Efiipanslixonf s reng ion,perresis o engt 0 Product lbs/sq. cent in 2 01108, 6 inches,

' in. inches it. lbs. inches A 24,100 1'. 5 a. 1 +0. 0023 B ..z 37, 650 0. 8 1. 26 0. 0107 It is evident that the new product is superior, its physical properties remaining practically conneaaoee stant under the extreme conditions of ten days exposure to water vapor at 95 C. whereas the product containing aluminum and magnesium shows considerable expansion and greater loss in'impact resistance and elongation under the same conditions of exposure to heat and humidity.

It is apparent that the new product has a very greatly increased utility more particularly for use where permanence in dimensions is required and where it would be subject to hot humid atmospheres. I

In the preparation of the new zinc base alloy product I prefer to use zinc of highest purity as is required for alloys containing aluminum, hut

v this is not essential although it is of considerable advantage and I mean to include as a part of this patent zinc base alloy products of composition stated prepared from zinc of high as well as commercial purity.

Having thus set forth the nature of my in-\ vention, what I claim is:

1. As anew article of manufacture a metallic product comprising a die casting made of a zinc base alloy consisting of from 0.05 percent to 10 percent manganese and the balance zinc metal containing 99.98 percent or more zinc.

2. As a new article of manufacture a metallic product comprising a die casting made of a zinc base alloy consisting of from 0.50 percent to 2.0 percent manganese and the balance zinc metal containing at least 99.98 percent zinc.

' JOHN R. FREEMAN, JR. 

